In my miata? I know its a silly question, but Its something worth asking. I was told 15w50 would be great, but I wanted to know what other people prefer. Especially people that occasionally track their car.
I have been using the Idemitsu Full Synthetic 10w-30. If it's good enough for a 13000 RPM Rotary it gives my Miata plenty of protection. I've never had any problems with Mobil,Castrol,Valvoline, or Royal Purple in the past. IMO all good oils and go with whatever is on sale at that time.